All CFI and MFI engines use the EEC system. The heart of the EEC system is a micro-processor called an Powertrain Control Module (PCM). The PCM receives data from a number of sensors and other electronic components (switches, relay, etc.). Based on information received and information programmed in the PCM's memory, it generates output signals to control various relay, solenoids and other actuators. The PCM in the EEC system has calibration modules located inside the assembly that contain calibration specifications for optimizing emissions, fuel economy and drive ability. The calibration module is called a PROM.
A potentiometer senses the position of the vane airflow meter in the engine's air induction system and generates a voltage signal that varies with the amount of air drawn into the engine. A sensor in the area of the vane airflow meter measures the temperature of the incoming air and transmits a corresponding electrical signal. Another temperature sensor inserted in the engine coolant tells if the engine is cold or warmed up. And a switch that senses throttle plate position produces electrical signals that tell the control unit when the throttle is closed or wide open.
A special probe (oxygen sensor) in the exhaust manifold measures the amount of oxygen in the exhaust gas, which is in indication of combustion efficiency, and sends a signal to the control unit. The sixth signal, crankshaft position information, is transmitted by a sensor integral with the new-design distributor.
The EEC microcomputer circuit processes the input signals and produces output control signals to the fuel injectors to regulate fuel discharged to the injectors. It also adjusts ignition spark timing to provide the best balance between driveability and economy.
Because of the complicated nature of the Ford system, special tools and procedures are necessary for testing and troubleshooting.